1. Field of the Invention
The invention concerns deep drilling systems and/or well pumping systems and associated apparatus for compensating for restoring torques introduced to a drive string of such a system by the driven end thereof.
2. Description of Related Technology
Several types of deep drilling devices and deep well pump devices are known in the art. A common feature to such devices is that a drive string is coupled to a drilling spindle or to the pump rotor, the string extending over a long distance and being driven by a driving motor. A deep drilling device may be used to prepare a borehole, into which a rotor and stator of a deep well pump device can then be introduced, for example, to pump oil. Owing to the length of the rotating components, e.g., a drive string and rotor, or a drive or drill string and drilling spindle, torsional forces occur in such systems during rotation, which are stored in these components over their length as restoring forces (sometimes identified as reactive forces). During an interruption of power flow from the driving motor to the driven end, for example, when the driving motor is disconnected, or in an emergency, torsion in the peripheral direction and torsional stress on the driven rotating components may lead to the release of a restoring torque through the rotating component, which then acts in the drive, particularly the driving motor and the components connected to it, for example, the connected gears of a driving motor. Such torque release can lead to significant and even irreversible damage, depending on the magnitude of the restoring torque. Such torque release may be particularly damaging if the driving motor is an electric drive motor, which can be driven backwards and thus damaged. Also, drive systems for the most part are not designed for such high, abrupt loads.
To solve these problems, U.S. Pat. No. 5,358,036 discloses a hydraulically operated disk brake device for a deep well pump device, which is disposed between a driving motor and a drive string being driven by the driving motor. The pressure required for activation is produced by a pump device. The pump device is disposed in the drive string so that it is brought into operation as a function of the direction of rotation of the string being driven by its torque and thus activates the brake disk device.
However, devices of the type disclosed in U.S. Pat. No. 5,358,036 are characterized by significant design demands and thus increased cost. The components that accomplish cushioning of the restoring torque and thus the braking effect are also subject to high wear because of mechanical stress.